1. Field of the Invention
The present invention relates generally to the field of surgical repair of retinal disorders, and more specifically to pneumatic Vitrectomy cutter power delivery during ophthalmic procedures such as the removal of vitreous gel.
2. Description of the Related Art
Vitrectomy surgery has been successfully employed in the treatment of certain ocular problems, such as retinal detachments, resulting from tears or holes in the retina. Vitrectomy surgery typically involves removal of vitreous gel and may utilize three small incisions in the pars plana of the patient's eye. These incisions allow the surgeon to pass three separate instruments into the patient's eye to affect the ocular procedure. The surgical instruments typically include a vitreous cutting device, an illumination source, and an infusion port. Current vitreous cutting devices may involve a “guillotine type action” where a small knife is used to remove the vitreous gel. Vitreous cutters are available in either electric or pneumatic form. Today's electric cutters may operate within a range of speeds typically between 750-2500 cuts-per-minute (CPM) where pneumatic cutters may operate within a range of speeds between speeds 400-2100 CPM. The surgeon or practitioner may adjust to control, by selecting or varying, the pneumatic vitrectomy surgical instrument cutting speed, i.e. the cutting device within the handpiece, sufficient to perform different activities during the corrective procedure. Corrective procedures may include: macular degeneration, retinal detachment, macular pucker, and eye injuries.
The cutting device within the handpiece requires precise control of the speed of the cutting blade. Today's systems typically employ a constant or fixed frequency control signal to open and close the valve resulting in fixed cyclic valve timing and a fixed, relatively rapid cutting speed. Input supply pressure is varied to achieve a desired cutting speed.
Designs based on varying the input supplying pressure to control the speed or rate of cutting are limited by how quickly the air volume in the cutter body and the associated tube set may be pressurized to reach the minimum peak pressure required to advance the cutter to a cut position and then vent to reach the minimum residual pressure to allow the spring-loaded cutter to return to a retracted position. Current pneumatic designs are limited to cutting speeds within a range of approximately 400 to 2100 cuts per minute.
Today's vitrectomy surgical systems require a wide range of selectable cutting speeds and highly accurate control of the amount of air pressure supplied to ensure proper instrument handpiece control and safe use in an operating theater. It may be beneficial in certain circumstances to offer the surgeon variations in cutting speeds, controllability, and options related to performing a vitrectomy procedure. Based on the foregoing, it would be advantageous to provide a system that enables pneumatic cutting functionality at cutting speeds at or higher than achievable with today's designs vitrectomy surgical instrument systems with varying options in effectuating the highest desired cutting speeds.